1. Field of the Invention
The present invention relates to cationic dye compounds and a method for increasing their solubility in organic solvents by associating them with fluorinated alkylsulfonyl anions.
2. Background of the Art
Compounds and materials having positively charged ions, cationic materials, tend to have poor solubility in many organic solvents. As many useful types of compositions are based on organic systems, either organic polymeric systems or organic resin systems, reduced solubility in organic systems limits the field of utility of many cationic materials. Amongst the cationic materials which could benefit from increased solubility in organic systems are photoinitiators (particularly those based on iodonium, sulfonium diazonium, and phosphonium salts and salts of organometallic complex cations), polymeric antistatic agents which are positively charged (especially fluorinated, quaternary, or phosphonium cationic materials), transition metal cations, and dyes (for example, as colorants, antihalation dyes, or spectral sensitizing dyes). It has been traditional, particularly in the organic dye art, to attempt to improve dye solubility in organic based compositions, particularly in non-polar organic solutions, by adding ballasting groups to the dye structure. Dye ballasting groups for organic systems are groups which extend from the cationic portion of the dye to increase the solubility of the compound in the solvent. Typical organic solvent ballasting groups would be longer chain alkyl groups.
Various anions have also been used to increase the solubility of cations and organic cationic materials in organic solutions. Amongst the more common anions used for this purpose are PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, RCO.sub.2.sup.-, RSO.sub.3.sup.-, ArSO.sub.3.sup.-, tetraphenyl borate, CIO.sub.4.sup.-, I.sup.-, I.sub.3.sup.-, BF.sub.4.sup.-, RArSO.sub.3.sup.-, and the like, where R is a straight chain, branched chain, or cyclic hydrocarbon or fluorinated hydrocarbon chain of 1-18 carbon atoms, and Ar is a phenyl or naphthyl group.
Although these anions did improve solubility of cations in organic solvents, the effect was often minimal in less polar solvents such a methyl ethyl ketone (MEK) where the solubility of the cation-anion salts is often on the order of only a few milligrams salt per gram of MEK. The fact that such small improvements have been recognized over the years as significant advantages is evidence of the need for further improvement in solubilization of cations in organic solvents and binders. It is often necessary during coating operations for the solubility of salts in the coating solutions to be on the order of 5-50 mg or more per gram of MEK. With the aforementioned anions, it was often necessary to resort to the use of more polar solvents (i.e., more polar than MEK) such as methanol, tetrahydrofuran, dimethylsulfoxide, etc. in combination with MEK to achieve desirable concentrations of cationic materials. The use of more polar solvents is known to sometimes lead to undesirable side effects as coating defects, haziness, or even crystallization of the salt in the dried coating (e.g., blooming of the salt from the dried layer).
Perfluoro-4-ethylcyclohexane sulfonate (known as the PECHS anion) is a fluorinated hydrocarbon sulfonated anion having a molecular weight of 461 which has been used as a counterion with cationic dyes to increase their solubility in organic solvents such as MEK (see for example U.S. Pat. Nos. 5,314,795 and 5,324,627). However, it has been noted that, at high dye loadings in organic binder solutions, the PECHS anion can cause coating defects such as fisheyes. The PECHS anion is also more expensive than many simpler anions.
Ar.sub.4 B.sup.-, in the form of tetrakis(pentafluorophenyl) borate has been reported as a counterion in the study of the photochemistry of cationic cyanine dyes by X. Yang, A. Zaitsev, B. Sauerwein, S. Murphy, and G. B. Schuster, J. Am. Chem. Soc., 1992, 114, pp. 793-794. Ar.sub.4 B.sup.-, in the form of tetrakis[3,5-bis(trifluoromethyl)phenylborate (TFPB) has been used as a counterion in near infrared (NIR) absorbing cyanine dyes used in laser optical recording media in JP 0157431. TFPB has also been used as a lipophilic stable anionic agent in the solvent extraction of alkali metal cations (e.g., Li, Na, K, Rb, and Cs) by H. Nishida, et al. Bull. Chem. Soc. Jpn, 1984, 57, pp. 2600-2604. This same anion has been used as-a phase transfer catalyst in diazo coupling reactions by H. Iwamoto, et al., Bull. Chem. Soc. Jpn., 1983, 57, pp. 796-801.
Initiator and catalyst salts having as the anionic portion a boron-centered anion have been reported in copending application U.S. Set. No. 08/097/279 filed Jul. 23, 1993, which is hereby incorporated by reference. The non-nucleophilic anion is of the formula: EQU [BArX.sup.2 X.sup.3 X.sup.4 ].sup.-
wherein:
B is boron in a valence state of 3; PA1 Ar is a halogen substituted aromatic hydrocarbon radical containing from about 6 to about 30 carbon atoms and may be linked to one or more X groups through a stable bridging group; and PA1 X.sup.2, X.sup.3 and X.sup.4 are radicals selected, independently, from the group consisting of halide radicals, hydrocarbyl radicals containing from 1 to about 30 carbon atoms, substituted hydrocarbyl radicals containing from 1 to about 30 carbon atoms, wherein one or more of the hydrogen atoms is replaced by a halogen atom, dialkylamido radicals, hydroxide, alkoxide and aryloxide radicals, hydrocarbyl-mercaptide and -carboxylate radicals, wherein the alkyl and aryl hydrocarbyl portions of the radicals contain from 1 to about 30
carbon atoms, and hydrocarbon substituted metal (organometalloid) radicals, wherein each hydrocarbyl substitution contains from 1 to about 20 carbon atoms and the metal is selected from Group IVA of the Periodic Table of the Elements (e.g., Si, Ge, Sn, etc.). These non-nucleophilic salts are reported to provide improved solubility. In the case where the non-nucleophilic salt is a photoinitiator, improvements in photoreactivity and wavelength response are often seen.
Bis(perfiuoroalkylsulfonyl)methides (e.g., U.S. Pat. Nos. 4,039,521; 4,049,861; 4,069,368; 4,100,134; 4,115,295, and 5,136,097) and bis(perfiuoroalkylsulfonyl)imides (e.g., U.S. Pat. Nos. 4,031,036; 4,387,222; 4,247,674; 4,429,093,) have been used as anions for catalysts and latent thermal catalysts. Other patents show improvements in the use of those anions and their synthesis, such as U.S. Pat. Nos. 3,704,311; 3,758,531; 3,758,591; 3,758,952; and 3,758,953; and J. N. Meussdorffer, et al., Chem.Ztg., 1972, 38, p. 582.
The thermal decomposition chemistry of a tris-(perfluoromethylsulfonyl)methide salt of benzene diazonium cation was studied by both Y. L. Yagupolskii, et al., J. Org. Chem. U.S.S.R. (Engl. Transl.), 1990, 26, 584-5; and S. Z. Zhu, et al., Inorg. Chem., 1993, 32, pp.223-226. The latter also studied the thermal decomposition chemistry of the bis(perfluoromethylsulfonyl)imide salt of a benzene diazonium cation.